The invention relates to a switchable coupling that is disposed between a driving element that is, for example, embodied as a pulley and an output element, wherein the switchable coupling includes a coupling system for creating a non-positive- and/or positive-locking connection between the driving element and the output element, as well as an actuator, preferably an electromagnetic actuator, a switching element in the operative vicinity of the actuator, as well as at least one elastic actuating element that is disposed between the output element and the switching element, and wherein the switching element is movable in an infinitely variable manner between a starting position via a central position as far as an end position, wherein, in the central position of the switching element, the switchable coupling has a different state (open or closed) than in the starting position, and wherein the elastic actuating element applies a force on the switching element in the direction of the starting position, and wherein the actuator only exercises forces on the switching element in the direction of the end position whose maximum value exceeds the force value of the elastic actuating element in any position.
Such preferably electromagnetically actuated couplings are known in the prior art. For example, European patent document EP 1378677 discloses a switchable coupling between a pulley as driving element and a shaft as output element. This switchable coupling also has an electromagnetic actuator whose force moves, in the state when current is applied, a switching element and further components of the coupling towards each other in such a manner that they are brought into a positive-locking engagement. Furthermore, this switchable coupling also includes an elastic actuating element that applies a spring force, countering the force of the actuator, to the switching element, such that, after the actuator has been switched off, the spring force moves the switching element out of engagement with the further parts of the coupling. Therefore, in the state “coupling=open” in this switchable coupling, the actuator is not active and does not consume energy. In the state “coupling=closed,” the actuator in this switchable coupling must, however, be permanently engaged and can then, as an electromagnetic actuator, be supplied with current, and wherein the actuator permanently consumes energy.
DE 1 575 762 also discloses an electromagnetic tooth clutch between a driving element and an output element. For the switching state “coupling=closed,” the electromagnetic actuator in this switchable coupling must also be permanently supplied with current. Although it is possible to reduce the magnetic force required therein by the shape of the switching teeth, complete cancellation is not possible.
German patent document DE 10331927 B3 discloses a clutch actuator for a switchable coupling between a driving element and an output element. In this coupling, preferably in use for utility vehicles, the clutch actuator does not act directly on the elastic actuating element of the coupling but on a transmission that reduces the required force in the clutch actuator for opening the coupling. Nonetheless, with this switchable coupling as well, the clutch actuator consumes energy to maintain the switchable coupling in the state “coupling=open.” When the energy supply to the clutch actuator is switched off, the elastic actuating element ultimately counteracts the force of the clutch actuator in this instance as well and switches the switchable coupling to the state “coupling=closed,” especially in the manner that is known, as a matter of principle, from most starting clutches in motor vehicles.
This prior art thus constitutes the basis for an initial partial object of the invention, which is to provide a switchable coupling that is able to maintain the two switching states “coupling=open” and “coupling=closed” without the supply and consumption of energy, and whose actuator uses energy only for the changeover between the two switching states.
A switchable coupling that achieves this partial object is disclosed in German patent document DE 102005001909 A1. Said coupling has an elastic actuating element that is a bistable spring and therefore able to assume two shapes. A switchable coupling having such a spring can be configured such that the switching states “coupling=open” and “coupling=closed” can be held stable without supplying energy to an actuator. However, switching such a coupling requires an actuator that is able to act on the bistable spring in two opposite directions of force.
According to this prior art, the above-captioned object shall be amended in such a manner that the switchable coupling must be configured such that the actuator thereof must only generate forces in one direction, thus making a single-side-operating actuator design, preferably an electromagnetic actuator, a possibility. This allows for the implementation of simple principles of operation, as well as the realization of savings in terms of construction space and costs.
German patent document DE 102005022218 A1 discloses a further relevant representative from the prior art regarding an actuating system for a switchable coupling. This switchable coupling has an actuator that acts only in one direction on a switching element of the coupling, specifically against the force of an elastic actuating element. In the closed state, this coupling is held by an automatically locking mechanism functioning according to the operative principle of a free-running roller or ball. However, to switch this switchable coupling from the switching state “coupling=closed” to the switching state of “coupling=open,” said coupling requires a second actuator in order to release the locking unit mechanism again.
Therefore, the underlying object of the present invention is the implementation of a switchable coupling that is able to maintain the two switching states “coupling=open” and “coupling=closed” without any supply or consumption of energy, and whose actuator must only generate forces for the changeover operation, specifically only in one direction, between the two switching states. The switchable coupling according to the invention shall also not need any additional actuating elements or further actuators for possibly needed locking unit mechanisms that may be required for holding certain switching states.
This object is achieved with a switchable coupling is disposed between a driving element and an output element and includes a coupling system for creating a non-positive- and/or positive-locking connection between the driving element and the output element, as well as, preferably, an electromagnetic actuator and a switching element in the operative vicinity of the actuator and at least one elastic actuating element that is disposed between the output element and the switching element, wherein the switching element is movable in an infinitely variable manner between a starting position and via a central position as far as an end position, and wherein the switchable coupling has a different state (open or closed) in the central position than in the starting position, and wherein the elastic actuating element applies a force on the switching element in the direction of the starting position, and wherein the actuator only applies forces on the switching element in the direction of the end position whose maximum value exceeds in each position the force value of the elastic actuating element, and according to the invention a locking unit is rotatably disposed in the circumferential direction on the output element or on parts connected to the output element but held in the axial direction between a first locking unit stop and a second locking unit stop, and wherein a rotational system is connected to the switching element or the locking unit that includes first operative surfaces that, with a movement of the switching element from a position shortly behind the central position to as far as the end position, come into contact with first slanting molded elements on the locking unit or first slanting molded elements on the switching element, thereby preloading first resilient rotational elements in such a manner that the locking unit is rotated by a first angular pitch in relation to the switching element, and wherein the rotational system includes second operative surfaces that, upon a movement of the switching element back from the end position to the central position, make contact with second slanting molded elements on the locking unit or second slanting molded elements on the switching element, thereby preloading second resilient rotational elements and rotating the locking unit in relation to the switching element by a second angular pitch.
The coupling according to the invention is thus to include a locking unit that locks a switching state in a manner that will be described below, or that makes a changeover process possible. To this end, however, the locking unit must assume different positions. Avoiding any need for using a separate actuator for this purpose, the locking unit is rotated by a rotational system, which is connected to the locking unit itself or a switching element, by the movement of the switching element that is generated by the actuator, if possible around the actuation axis of the switching element.
In a further embodiment of the invention, after a first movement of the switching element from the starting position to the end position and back to the central position, the switching element assumes a first relative position in the circumferential direction in relation to the switching element in which, in the central position, the switching element makes contact in the axial operative direction with a locking unit stop on the locking unit. The locking unit further includes second positive-locking retaining elements, and the switching element also has second positive-locking retaining elements that are engaged with each other in this central position fixing this first relative position in place in the circumferential direction.
With a first actuation of the actuator, the actuator acts, applying a force on the switching element, such that the switching element is moved against the force of the elastic actuation element in the axial direction from the starting position thereof and as far as an end position, and the locking unit is rotated therein by a first angular pitch. The actuator is then deactivated, and the elastic actuation element returns the switching element to the central position. The locking unit is therein rotated by a second angular pitch. The locking unit is now in a relative position in relation to the switching element that the switching element is in contact by a switching element stop thereof with a first locking unit stop of the locking unit. This way, any further movement by the switching element in the direction of the starting position is locked. Second positive-locking retaining elements on the locking unit and on the switching element prevent that this relative position changes inadvertently in the circumferential direction between the locking unit and switching element, for example due to vibrations occurring in the switchable coupling.
To ensure that, following re-activation of the actuator, the switching element can be moved to the starting position, the locking unit includes locking grooves. Following a second movement of the switching element from the central position as far as to the end position and back to the central position, the locking unit assumes a second relative position in relation to the switching element in the circumferential direction in which, starting from the central position, the switching element with all of the molded elements thereof is able to glide, without impediment, through the locking unit grooves in the locking unit, specifically as far as to the starting position in which the switching element makes contact with the starting stop. Furthermore, the locking unit includes third positive-locking retaining elements of the locking unit, and the switching element includes third positive-locking retaining elements of the switching element that, in this second relative position, are engaged with each other in each axial position of the switching element between the central position and the starting position, whereby they fix said relative position in place in the circumferential direction.
To ensure that after each actuation of the actuator and the thus resulting movement of the switching element to the end position, subsequently followed by the return movement to the central position, and that, after the actuator has been switched off, the first, and second positions are alternating between the switching element and the locking unit in the circumferential direction, it is envisioned according to the invention to offset the first relative position and the second relative position between the switching element and the locking unit by an angular pitch, respectively, in the circumferential direction, and in that the first angular pitch and the second angular pitch result together in this overall angular pitch, and in that this overall angular pitch is an even-numbered angular pitch of 360°. Preferably, the first angular pitch and the second angular pitch are of equal sizes, thereby each constituting half the size of the overall angular pitch.
The cyclical rotation of the locking unit in relation to the switching element occurs due to a first partial rotation by the first angular pitch, when the switching element moves from the central position to the end position, and due to a second partial rotation by the second angular pitch, when the switching element moves from the end position to the central position. To prevent that the locking unit performs a reverse rotation by the same second angular pitch after the second partial rotation, when the switching element moves next from the central position to the end position, it is provided according to the invention that, when the switching element is located in the central position, the first operative surfaces of the rotational system are disengaged from the switching element or the locking unit, whereby the first resilient rotational elements are relaxed. To prevent that the locking unit performs a reverse rotation by the same first angular pitch after the first partial rotation, when the switching element moves next from the end position to the central position, it is provided according to the invention that, when the switching element is located in the end position, the second operative surfaces of the rotational system are disengaged from the switching element or the locking unit, whereby the second resilient rotational elements are relaxed.
A geometric requirement for the correct cyclical rotation is, furthermore, that the overall angular pitch between the first positive-locking retaining elements and the second positive-locking retaining elements on the switching element, minus the offset angle between the first positive-locking retaining elements and the second positive-locking retaining elements on the locking unit, plus the first angular pitch or minus the second angular pitch is a whole-numbered multiple of the angular pitch between the first relative position and the second relative position.
Finally, it is also envisioned according to the invention that, when the switching element is located in the end position, first positive-locking retaining elements on the locking unit are engaged with first positive-locking retaining elements on the switching element fixing in place in the circumferential direction the relative position of the switching element and the locking unit in this switching position. By the different retaining elements it is ensured that, following rotations by certain angular pitches and during the relaxing of the resilient rotational elements, the locking unit does not inadvertently change position in relation to the switching element, for example due to oscillations and vibrations in the switchable coupling.
The invention is not limited to the characteristics of the associated claims. Possibilities involving combinations of individual characteristics of claims and combinations of individual characteristics of claims with the information as to advantages and disclosures in the embodiments are conceivable and envisioned. The invention also relates particularly to solutions that operate in the manner of the prior art, some of which have already been described previously in the embodiments.
Three embodiments of the switchable coupling according to the invention will be described below in an exemplary manner on the basis of FIGS. 1 to 20 and explained in terms of the arrangement of the elements of the coupling and the related functionalities thereof. FIGS. 1 to 12 therein relate to a first embodied variant involving a tooth clutch and friction clutch that will presently be described in special detail.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.